The US Centers for Disease Control and Prevention on Sunday confirmed that four people in New Hampshire have fungal infections linked to a meningitis outbreak that has swelled to more than 200 confirmed cases nationwide and claimed the lives of 15 people.

Three patients have fungal meningitis — an inflammation of the brain — and a fourth person has a peripheral joint infection, according to the CDC, and all cases are related to apparently tainted steroids produced by a Framingham facility.

The New Hampshire patients are between the ages of 40 and 60 and are the first confirmed victims of the outbreak in New England.

The three men and one woman who were infected in New Hampshire received steroid injections from PainCare LLC, a pain management practice that obtained the product from the compounding center.

Dr. Michael O’Connell, PainCare’s chief executive officer, said Sunday that three of the patients are being treated at various hospitals in New Hampshire, but he had no word on their conditions, though they did not appear to have life threatening complications. One man who was infected has been treated and released.

PainCare has identified 741 patients who may have been exposed to the contaminated steroid, but O’Connell said that number could grow.

“We feel it’s quite likely that there will be more cases that will be identified as related to the exposure to the tainted product,” O’Connell said. “I don’t see how that could not be the case.”

He said providers and patients at PainCare, which is the only known company in the state to have used the tainted product, have been under considerable stress.

“Everyone has been putting in many, many extra hours,” O’Connell said. “Not only in evaluating and ... [performing] diagnostic testing of patients, but they also have been putting in more hours on call, taking calls from patients who are worried and in distress.”

He said of the patients, “They are beside themselves.”

As the number of confirmed cases related to the outbreak continued to grow, the CDC on Sunday issued updated guidelines for doctors in treating affected patients.

O’Connell said it is difficult to determine the best course of action for patients, some of whom show symptoms, even though their initial test results came back normal.

“That’s why it’s important that the patients not just be seen once but ... [also] repeat some of the diagnostic testing,” he said.

Fungal meningitis is not transmitted from person to person. However, any patients who have received an epidural steroid injection since May 21 should contact their doctors if they experience any one of several symptoms, according to the CDC.

Those symptoms are new or worsening headaches; fever; sensitivity to light; neck stiffness; new weakness or numbness; slurred speech; or increased pain, redness or swelling at the point of the injection.

The CDC confirmed Sunday on its website that the New Hampshire patients are four of the 205 infections nationwide that are tied to the outbreak, which now spans 14 states. Fifteen people have died.

New Hampshire’s Department of Health and Human Services has said the product that is believed to be behind the outbreak was distributed at PainCare locations in Somersworth, Merrimack, and Newington.

A spokeswoman for the department could not be reached for comment on Sunday.

David Kibbe, a spokesman for the Massachusetts Department of Public Health, said in a statement that the agency has worked with federal officials to notify all states that were potentially affected, and the parties are continuing to share information as the investigation progresses.

“None of the three contaminated lots were shipped to Massachusetts locations and there are no cases in the Commonwealth,” Kibbe said.

Besides New Hampshire, the other New England states to receive the recalled product from the compounding center are Rhode Island and Connecticutt, according to the CDC.

The Rhode Island Department of Health had no reported cases as of Sunday, a spokeswoman said.